Means for transmission of force by liquid pressure



u8 4, 1931- R. T. KNAPP 1,817-315 MEANS FOR TRANSMISSION OF FORCE BY LIQUID PRESSURE original Fned June 11, 192s sheets-sheet 1 Aug. 4, 1931. R. T. KNAPP 1,817,315

MEANS FOR TRANSMISSION 01;' FORCE BY LIQUID PRESSURE original Filed June'll. 192e 2 sheets-sheet 2 B Y/L y A TTOR E Ys Eil Patented Aug. 4, 1931 UNITED STATES PATENT OFFICE ROBERT T. KNAPP, 0F RIVERSIDE, CALIFORNIA, ASSIGNOR TO RIVERSIDE CEMENT COMPANY, 0F LOSANGELES, CALIFORNIA, A CORPORATION OF DELAWARE MEANS FOR TRANSMISSION OF FORCE BY LIQUID PRESSURE Original application. filed June 11, 1928, Serial' No. 284,316. Divided and this application filed September 14, 1929. Serial No. 392,667.

This application is a division of my application Ser. No. 284,316, filed June 11, 1928 for Apparatus for continuous weighing of materials. The claims of the parent application are directed entirely to continuous weighing means. Force transmitting means of' the type herein described and claimed are shown and described in the parent applica-A tion, for use in obtaining a measurement of the weight, and are included iny some of the claims. The claims of this divisional application, 0n the other hand, are restricted entirely to the force transmitting means itself, without regard to the use toy which the same is put.

This invention relates to the transmission of mechanical force or power `by the` agency of liquid pressure and is particularly adapted for use in connection with the employment of liquid pressure systems for measuring mechanical forces of various kinds, such as weight, pressure, or thev like. The principal object of the invention is to provide'means for automatically compensating for variations in temperature of the liquid utilized for transmission of the force.

The pressure in a confined liquid affords a very convenient and accurate means for transmission of a certain mechanical force from one point to another. However, it has been found that variations in temperature seriously affect the results obtained, on account of the tendency of the pressure in a confined liquid to vary with the temperature, unless proper means are provided forcompensation therefor. The principal purpose of this invention, therefore, is to provide tem# perature responsive means connected to the fluid pressureconfining system andr adapted to vary the volume of such liquid confining system upon variations in temperature, the variation in volume being such as to maintain the pressure constant regardless of such variations in temperature.

A furtherobject of the invention isto provide improved means for creating liquid pressure by the action of mechanical force.

The accompanying drawings illustrate an embodimentof my invention and the utilization thereof in connection with a continuous weighing apparatus such as shown in my aforesaid application, and referring thereto: Fig. 1 is a side elevation of my improved device for creating liquid pressure by the action of mechanical force, with a temperature compensating device according to my invention connected thereto.

Fig. 2 is a plan view of the parts shown in Fig. 1.

Fig. 3 is a vertical section on lin-e 3 3 in Fig. 1.

Fig. 4 is a vertical section on line 4-4 in Fig. 2.

Fig. 5 is a vertical section on line 5-5 in Fig. 1.

Fig. 6 is a perspective view of an apparatus for the continuous weighing of materials, showing the use of liquid pressure means according to my invention in connection therewith.

The liquid pressure force transmitting system is shown as including a liquid pressure creating device 1 adapted to be subject-ed to a mechanical force and to create variable liquid pressure therein in response to variations of such force, and a measuring (recording or indicating) device 2 connected by pipe 3 to said pressure creating device so as to be operated by the resulti variations in liquid pressure. The pressure creating device 1 is shown as comprising a cylindrical casing 5 supported by bracket 6 or other suitable fixed supporting means and ametaly bellows element 7 rigidly secured at one end to a normally fixed head member 8 and connected at its otherend to an end plate 9. Said end plate is provided with a bearingmember of relatively small surface, such as a ste-el ball 11 adapted to be engaged by any suitable means, such as bar 12 for application of mechanical force thereto. The bellows element 7 may be formed lof any suitable flexible metal, such as brass or copper, and is sufliciently thin walled to provide the desired flexibility.

The bellows element may advantageously be provided with means for holding the head mcmb-er 8 in fixed position against any force of a magnitude such as is to be transmitted by the system, while permitting such head member to yield in the event of application CII Y tubirml I,-

of an excessive force to the bellows element, in order to preventdamage to said bellows element. For this purpose a coiled compression spring* 14 may be provided between the head member and a relatively lixed head member l5. threaded stem 1G, formed inh or secured to the head member movable through opening' l? in d loclr nuts er collars i3 are d stem and are dapted to ai'iut auainw the outer face 01 membe' l5. By tighten un en the adjusting collars any desired comi .i may be appiicd to soi-nrT 14. such npression being; so adjuster tnat l "han that intended to oe transe system is required to el'lect anv lfurther ctunpression or said spring. The en"l member at tie bottom ot thc bellows element is pero tted to move throughout a range corrdrzionding to ail normal movenieiis oinA the l element due to applicawithin the range to be trans- 1 A are stop means are refierablg.v provided tor limiting' the vard vement o said member upon apinieaticn 'i' excessive torce thereto. For this purpose the member 9 may be provided with a tapered or inclined face i9 adapted to er 5 y e a similarly tapered ox inciined seat 2l at the lower end of c vlindL cal easing The amount oi' movement of member 9 which is permitted before engouement with seat 2l may be adjusted by screwinu' head l5 into or out of the cylindrical ca n y o in which it is threadediy mounted as sho n at 22.

The pressure responsive device, operable by pi sure ansmitted thereto from the pressure creatii device. is shown as comprisiid pi are gauge of 'the recording 'cjaid aan is provided with an arm pirated at e oro itled at its outer end wit i other rece ding eiement oe a curve or record upon a rotatabiv mounted wiliin caf-unfit 2T and operated by suitabie cloci-worli mechanism in the usual manner of such devices. It will be tui-ther underst' f i that said gan-'1e may be provided with f VErable or form of pr ure resiA ve eiement oper tivelv conied to arm 25 and having a-liquid rcceiv space connef l bv tubing; 3 to a passage 25 ieading' through stein lo to the interior ot' he bellows element is i ot material sui'iiciently roue' and rigid o withstand any lio uid presv4 si deveioped within said bellow-f dement without deformation of the walls such tubing'.

In order to compensate for variations in volume oi the liquid in the system duo to changes in temperature and thus prerent such temperature changes 'from eti'cctiug the pressure. suitable teinjurature responsive coinpensafine` means arV provir'led tor automatically `varying the volume oit the liquid conrii e finingr system in proportion to the variation in the volume of the liquid atconstant pressure. Such means may comprise7 as shown particularly in Figs. l. 2, 4 and 5, a small bellows element 3l similar to the bellows element 7, secured between end members 32 and The member may be provided with the stem 34 connected to a branch 3a of the tubing 3, a passage 35 leadingr through said stem to establish communication between said tubing and the interior of the bellows element 3l. The end member 33 may be provided with a boss 3G to which are secured two parallel bars 3T of a metal having a relatively low temperature coellicient of expansion. Said bars may, for example, be formed of invar metal which has substantially zero coeliicient of expansion within the ordinary range of temperatures. Two other bars 3S, formed of some metal such as aluminum hav ing a higher coel'licient ot' expansion than the bars 37. are secured at one end to a fixed plate 39. said plate 39 being mounted in any suit# able manner upon bracket 6. At a suitable distance from the plate 39, the bars 3S are com nected by clamping means 41 to the bars 37, and in order to permit adjustment of said clamping means the same may be split or slotted as indicated at 42 and provided with suitable tightening bolts 43 so as to clamp the bars 37 and 38 tightly between the several sections of said clamping means when said bolts are tightened but to permit the clamping means to be moved inwardly and outwardly upon the bars when said bolts are loosened. The effective length of bars 3S may thus be adjusted so as to produce any desired rate of change .of volume of the bellows element 31 with changes in temperature.

The length of the bellows element 3l and consequently its volume at any giveny temperature. is also preferably adjustable. For this purpose the stem 34 may be threaded and a screw collar 45 may be provided thereon, said collar bearing against the face of plate 39 and hav/ineT an externally threaded stem portion 46 projecting through an opening 4T in said plate. A second screw collar 4S is threadedly mounted on the projecting stem port-ion 46 at the other side of said plate from the collar The collar 45 may be screwed in or .out on stem 34 to any desired position and the collar 48 may then be tightened to clamp plate 39 between the two collars. The position of the outer ends of the bellows element 3l being fixed by the position of clamping means 4l on the arms 37 and 3S. this ad` justment of collars 45 and 48 determines the position of the inner end or" the bellows element and consequently the cubical contents the cot A lock nut 49 may also be threadedly mounted on stem 34 to hold the coliar 45 in adjusted position thereon.

Tube 3, the interior of bellows elements 7 and 3l, and the passages 28 and 35 connecting said tubing to said bellows elements, as well as the pressure element of the recording ygauge 2, are all completely filled with wat-er or any. other suitableliquid. Short branch tubes 3?) and 3c arealso shown, one for connection to a vacuum pump for exhausting the air from the system and the other for connection to means for supplying water or other liquid thereto, said branch tubes being thereafter sealed ott' in any suitable manner.

The member 12, which is adapted to exert an upward thrust against the lower end of the pressure creating device 1 may be a member operated by any force which it is desired to n easure. In the present instance such member is shown as connected to an appa.- ratus tor the continuous weighing of inaterials, the upward thrust exerted thereby being dependent on the weight of material passing over such apparatus. Such continuous weighing apparatus is shown' as comprising balance means including a trame 51 consisting of two side members 51a connected together' by an end member 51?), said frame being pivotally supported on a shaft- 52 extending through bearing means 53 on the respective side members 54e of a fixed supporting frame 54, said fixed supporting frame 'further comprising an end member 542) connecting togetherthe two side members thereof` Said fixed supporting frame may be mounted on any suitable support, such as a concrete floor indicated at conveying means, consisting for example of a short endless conveyor belt 57, runs over pulleys 58 and 59. The'pulley 58 is shown as mounted in bearing means 60 on the side members 51a while the pulley 59 mounted on bearing blocks. 61 slidingk in grooves 62 in said side members and provided with spring for pressing outwardly on said bearing blocks to maintain the desired tension on the conveyor belt 57 at all times. A constant speed electric motor Gl is mounted upon a supporting platform G5 connected to the side frame members 51a and is conneeted through suitable reducing gear means indicated at GG to shaft G7 which is in turn connected through sprocket 63, chain G9 and sprocket with the conveyor drive pulley Mean-.1; are provided for delivering the material to be r-/eighe-fl onto the conveying member 7 directly above the pivotal supporting shalt oi the balance means. Such delivering means may comprise, for example,

al is delivered to any suitable means. For example, such material may pass through opening 76 in the Iioor into chute 77 for conducting the same to any desired point.

. In the operation of the appara tus above described, the material to be weighed, consisting for example of powdered or crushed material, is delivered through chute 72 onto the conveyor belt 57 directly above the pivotal supporting shaft 52. Such material is carried away by the belt and delivered through opening 76 and chute 77. The weight of the material on the conveyor belt at any instant exerts a turning moment upon the balance means which tends to raise the other end of said balance means. The member 12, which is shown as connected to the end frame member 515 of the balance means is thus caused to exert a force against'the lower end member 9 of the pressure creating device and compress the bellows element 7. The pressure througout the confined body of liquid is thus increased, such pressure being communicated through tubing to the pressure recording means 2 and causing corresponding movement of arm so that the recording means on said arm inscribes a record of the pressure in the system, in the well known manner of such recording devices. It will be seen that the pressure thus created by the bellows element and communicated through pipe 3 and recorded by the recording device 2 is dependent upon the upward thrust exerted by member 12 and hence upon the weight of material on the conveyor belt, so that the curve traced by the recording device furnishes a record of the weight of material passing over the balance means during any certain time interval. The bellows element 7 may be of such dimensions in proportion to the total volume of the liquid system that only slight movement ot' the end member 9 is required to produce considerable variation in liquid pressure, sutlicient to move the arm 25 of the recording device through its entire range of movement. In case an excessive weight should be inadvertently applied to the balance means, or if for any other reason the thrust member 12 should be forced upwardly with a greater force than that intended to be transmitted by the liquid pressure, the-spring 14 will yield upwardly under such excessive force and prevent damage to the bellows element. Moreover, when such excessive force becomes sufficient to compress spring 14 to a certain extent, the end member 9 will be brought into engagement with seat 21, thus preventing any further operation of the pressure creating device. It will be seen that the spring 14 and the stop means provided by seat 21 constitute important factors in the prevention of injury to the bellows element or to other parts of the apparatus.

In case of variations in temperature due, for example, to changes in the atmospheric l; the bars '37 temperature surrounding the apparatus7 the temperature compensating device vvill automat?.call),v comi; tor auch Vvariation in temperature and prevent the same trom h ving any eii'ect on the pressure in the liquid confining` system. For example, in case of increase in teu 'ature the bars ou, having a hierher coellic t of expansion, ivill undergo a iter increase in length than the bars 37, and since said bars are tied together bv the clanipiuo' means ll, the bel-lows element 3l will thus be elongated causing an increase in volume in the interior thereof T his increase in volume is just sutlicient to permit sullicient eiqiansion o'l the liquid in the s( tem so as to maint-ain the pressure thereof constant inso'iiar as any ellect ot temperature thereon is concerned. ivill be evident by moving the clamping' mea is il inivardli7 or outwardly on and 33? the length of bars 3S between said clamping means and the lined supporting' plate 32) ma),y be so adjusted as to cause any desired rate oi' elongation or contraction ot' the belloivs element with variations in tem peratu re so as to provide the automatic compensation as above described.

lVhile I have shon'n the liquid pressure force transmittingsr means employed in connection with a ucraini; a pparatus. and operating a recording gauge, it is evident that it ma.v also be used for other purposes where it is t sired to obtain an accurate indication or record of a variable mechanical force, at a point removed from the. point where such force is exerted. In general the pressure creating device l ma()r be mounted for actuation by any member adapted to exert a mechanical 'torce thereon, While the pres-sure responsive device ma)v be an)v device ha vingv a member movable b v variations in the liquid e delivered thereto. In

ill

an)v such ie conlincd liquidl acts as f l uismitting variations in 1 L force7 through the agencv of liquil pressiu'e, uch pressure beinfcr again re-converted to a other end of the s I claim:

l. An apparatus tor transmission of force by liquid pressure comprising:r means confining' a both.VY of liquid, means operable by mechanical torce to vary the pressure in said body ot' liquid, pressure responsive means operable by the pressure in said body mechanical force at the 'liquid and temperature responsive means connected to said liuuid confining means and operable to automaticallifv varv the volume thereof, upon variation in temperaturey the variation in volume being;` such as to prevent substantial 'ariation in pressure in the bodv of liquid by reason of such variation in teniperature.

Q. In combination ivith al liquid pressure system for transmission of mechanical force, a temperature compensating device connected to said liquid pressure system and operable in response to variation in temperature to automaticall7 varv the volume of the liquid contained in said system and prevent substantial variation in pressure in said tem due to such temperature variation.

A temperature compensating de ice for liquid pressure systems comprising means including a chambeu means connectingl said chamber to said liquid pressure system7 and means ope able in response to variation in temperature to a utomaticall ,v produce a variation in volume ot said chamber substantially proportional to the variation in temperature.

A temperature compensatingl device for fluid pressure 'force transmitting systems comprising a bellows element, members of relativel)T l gh and relativelyv lo\v temperature Coeli" ients of expansion connected to the respective ends of said bellows element7 and means connecting together said members at points removed from the connection thereof to said bellows element.

A device set forth in claim .4f and conn prising in additioin means for adj usting the position of said connecting means on said members with respect to said bellows element.

A device as set forth in claim el and compristine', in addition. means for adjusting said bellows element with respect to said members.

7. A device for creating; fluid pressure in response to the action ot mechanical torce comprising a bellows element provided with end members, one oi said end members being adapted for application ot' mechanical force thereto.` and` means engaging the other of said end members` and rcsilientlvY opposing; the. mechanical torce to be applief'l-to said first named end member, the (qniosinv force of said resilient meansy beine` lureuter than the mechanical forces under which the device is normally intended to operate.

8. A device for creatingr l" `id pressure bv the action of mechanical force comprisinglr .a bellows element havingf relativelv fixed and relatively movable end membersR said relativelyv movable end member beine' adapted for action of mechanical torce tlr 'cacrfiinst to compress said bellows element` and fixed stop means in position to be engaj'cd bv said movable end member upon a certain inovementof said end member in excess ot the normal movement thereof under mechanical forces under which the device is intended to operate.

In testimomv u'hereot' I have hereunto subscribed mj; name this lst dav of August. 1929.

RUPERT T. lNiiPl?. 

